The present invention relates to a switch unit for electric hand-tools, comprising a switch housing with switching means arranged therein, a carriage which is arranged movably in the housing and which is drivable by a trigger connected thereto, wherein the carriage is provided with at least one slider for sliding over a potentiometer track and with at least one movable contact of a mechanical switch.
Such switches are generally known.
To be able to compete with the generally decreasing price levels of these switches, optimal flexibility in the construction and the design of the switches is required. Manufacturers of electric hand tools generally order with short notice, and they often decide on amendments in the design of those switches at a late stage.
To be able to cope with these requirements, the aim of the invention is to provide a switch unit for such applications, which can be composed of several more or less standard components, and which can be assembled from those components according to need.
Therefore, the invention provides a switch unit, wherein the switch housing of the switch unit is divided into two parts, wherein the fixed contacts of the mechanical switch are arranged on a first part and the potentiometer track and the electronic components related thereto are arranged on the second part of the switch housing.
These features provide a possibility to adapt both sides of the housing to the requirements of the tool in which it is to be inserted, such as the type of electric supply, electric power level, range of switching, or type of semiconductor to be used for power control. By having all these different possibilities available in the second half of the housing, the requirements can be met by choice. Although the possibilities of choice appear the most in DC power, the invention is not limited to DC-control; it is just as well applicable to AC-control.
Due to the separation between electronic functions and switching, wherein for the operation of both functions use is made of the same movable element, i.e., the carriage, a degree of separation of functions is obtained without the space-saving integration of the switch being negated.
It is of course possible herein for both the slider and the operating element for the switching functions to be arranged on one side of the carriage, but it is equally possible for the slider and the contact to be arranged on either side of the carriage, and for the potentiometer track and the fixed switching contacts of the switch to be arranged on the relevant inner sides of the housing. This latter possibility would generally seem to be structurally more attractive.
According to another preferred embodiment, the switch unit includes an adaptation module. Between the switch housing and the adaptation module, the switch housing is provided with electrical connecting means which, when the adaptation module is arranged on the switch housing, are adapted to form an electrical connection.
This feature provides the possibility to include an additional switching function in such a switch unit. An example of such an extra switching function is reversing polarity to cause the electric motor of electric hand-tools to rotate in the other direction, for instance in drilling or screwing machines.
Another example of such a function is the adaptation to an electrical connection with the motor and the field winding or with the battery or the mains connection. Many types of connections are applied for this purpose. In this diversity of connecting methods, such as screw clamps, plug clamps, soldered connections, spring loaded contacts, connections and so on, the design of the contacts of the switch must always be adapted.
These measures have the result that a switch housing with the switching means arranged therein can be adapted, by connecting a module thereto, to provide an additional switch function and to adapt to a specific method of connection of the wires to be connected to the switch.
It is further attractive when at least the first part of the housing of the switch is manufactured from plastic and at least a number of the fixed contacts and the conductors connected thereto are embodied integrally and arranged in the plastic.
This saves a large number of fitting operations.
According to yet another preferred embodiment, the switch unit comprises a number of heat generating components and at least a part of the number thereof is mounted on a flat carrier, and the carrier is located between the second part of the switch housing and the path of the slider.
In principle, it is herein possible to make use of specific plastics suitable for this purpose, although it is also possible to make use of ceramic material, metal, metal oxides and the like.
According to another embodiment, the second part of the switch housing is made from metal.
Particularly in the application of a switch in an electric hand-tool, which is powered by a battery, such a switch usually comprises at least one component in which a considerable quantity of heat is generated. It is attractive to place such a component on a metal carrier, since metal is a good heat conductor. This provides the option of including in the carrier the function of a cooling plate in the calculation of the heat dissipation of the components placed on the carrier.
A dual function of the carrier is thereby obtained, that is the actual carrier function, a housing function, and a cooling plate function.
In another embodiment, the second part of the switch housing is made from plastic, and between the carrier and the second part of the switch housing, a metal plate is inserted.
The carrier is preferably provided with cooling ribs arranged on the outside.
In order to complete the modular system, it is attractive to make use of the same switch for different dimensions, that is for circuits with high heat dissipation and circuits with a lower heat dissipation. It is therefore attractive in the case of components with a high heat dissipation to make use of a metal carrier and in the case of other circuits to make use of a plastic carrier.
The measure that the metal carrier corresponds with a housing half provides the possibility of easy replacement thereof by a housing half of another material, for instance plastic. It is also possible herein to arrange the carrier in the relevant housing half, for instance by means of a snap connection.
It is of course essential for the module to be connected not only mechanically but also electrically to the switch housing and the switching means present therein. It is attractive for this purpose when the switch housing is adapted to make spring loaded connections for electrical contact with the module.
It will be apparent that this limits the amount of fitting work considerably. The operation of joining together the switch housing and module for placing thereon can after all be readily carried out by a mechanical process.
Since the module, which is adapted to execute an additional switching function, must of course also not only be connected to the actual switch housing, but also provided with external connections, it is attractive when a module is adapted to perform an additional switching function and is adapted to make plug connections for electrical contact with the switch and with a further module to be arranged on the module.
This further module then serves to connect the external connections.
An example of an additional switching function which can be performed in a module is the function of a polarity reversal module.
The additional, electrical switching function is however certainly not limited to this polarity reversal function. It is equally possible to add other additional functions, such as that of a mains filter.
A module is preferably formed by a connecting module which is adapted to make a plug connection to the switch or another module, and which is provided with connecting means for making an external connection.
This measure provides the option of adapting a switch to the method of attachment of the external connections without making structural changes to the actual switch. Modules can herein be envisaged which are adapted to make a solder connection for a socket joint, a screw clamp connection and the like.
The measures described heretofore relate only to external functions, which are separated per se from the actual switch.